Modern motor vehicles are equipped with so-called on-board diagnostic systems because of statutorily mandated requirements. With the aid of these systems, the operability of exhaust-gas relevant vehicle component systems is monitored. One example of such a system is a tank-venting system having an active charcoal filter, a controllable tank-venting valve as well as associated line connections. An apparatus for on-board diagnosis of a tank-venting valve is described, for example, in U.S. Pat. No. 4,794,790.
It is customary to check these systems when first taking the vehicle into service with the aid of the on-board diagnostic functions. For this purpose, a driving curve of operating points having predetermined values of load, rpm and other parameters, if required, is run through under defined conditions on a test stand. The drive curve is so defined that the on-board diagnostic programs run through automatically. If an exhaust-gas relevant fault is registered, then this is stored as a fault announcement in the control apparatus and is signalized to the outside during or after the test run, for example, via an external tester so that measures can be taken to eliminate the fault.
The read-out of self-testing data in combination with a control at the end of the assembly line is, for example, known from VDI Berichten 612, page 392. The system presented there relates to the expansion of existing control apparatus with a suitable interface for the purpose of making the data of the self test of the control apparatus, for example, understandable to a service technician.
A high expenditure of time is associated with carrying out a driving curve which is adequate for triggering and carrying out the on-board diagnostic functions. This is so because the diagnostic functions designed for everyday operation are triggered by the control apparatus, for example, only after the elapse of a certain time span after the start of the vehicle. This time span can be in the range of minutes which is a very long time span for a test at the end of an assembly line.